Proton exchange membrane fuel cell (PEMFC) is a renewable energy source rapidly approaching commercial viability. The performance is significantly affected by the transfer of fluid, charges, and heat; gas diffusion layer (GDL) is primarily concerned with the consistent transfer of these components, which are heavily influenced by the material and design. High-efficiency GDL must have excellent thermal conductivity, electrical conductivity, permeability, corrosion resistance, and high mechanical characteristics. The first step in creating a high-performance GDL is selecting the appropriate material. Therefore, titanium is a suitable substitute for steel or carbon due to its high strength-to-weight and superior corrosion resistance. The second crucial parameter is the fabrication method that governs all the properties. This review seeks to comprehend numerous fabrication methods such as tape casting, 3D printing, freeze casting, phase separation technique, and lithography, along with the porosity controller in each process such as partial sintering, input design, ice structure, pore agent, etching time, and mask width. Moreover, other GDL properties are being studied, including microstructure and morphology. In the future, GeoDict simulation is highly recommended for optimizing various GDL properties, as it is frequently used for other porous materials. The approach can save time and energy compared to intensive experimental work.

The Republic of Korea is one of the largest consumers and a leading exporter of electronics, medical appliances, and heavy and light vehicles. Rare-earth (RE)-based magnets are indispensable for these technologies, and Korea is totally dependent on imports of compounds or composites of REEs, as the country lacks natural resources. Effect on rare earth supply chain significantly affects Korea’s transition towards a green economy. This study investigates the Republic of Korea’s approach to developing a secure rare earth supply chain for REE magnets via a recycling and materialization process known as ReMaT. It investigates the progress Korea has made so far regarding ReMaT from both technical and non-technical perspectives. Rare earth elements are successfully recycled as part of this process while experiments at the industrial scale is carried out. In this paper, the research results in terms of the extraction efficiency of rare earth elements are discussed and a comparison with previous relevant studies is provided. This study also highlights the opportunities and challenges regarding the implementation of the ReMaT process in order to create a downstream rare earth value chain based on circular economy principles.

The coupled system of multi-degrees of freedom, such as charge, spin, orbital and lattice, has recently received much attention due to its potential to improve the magnetocaloric effect (MCE). The exotic inverse MCE was observed in rare-earth tetraborides of Ho_1-xDy_xB₄ (x = 0.0, 0.5, and 1.0), associated with a strong coupling between magnetic dipoles and orbital quadrupoles in the strong spin-orbit coupling and geometric frustration. Here, the magnetism and magnetocaloric effects of ErB₄ and TmB₄ are investigated. It shows the maximum entropy changes of 11.4 J/kgK, and 12.6 J/kgK with the field of ΔH ≈ 40 kOe (H∥c) in ErB₄ and TmB₄, respectively. The field- and temperature-dependence of the entropy change is found to be quite different from those of the conventional MCE. And the entropy change is also found to have strong correlation with the field induced meta-magnetic transition. Because the field induced transition is due to magnetic moment reorientation, which is strongly coupled with quadrupole moment, the abnormal MCE of ErB₄ and TmB₄ is attributed to the dipole-quadrupole interaction and magnetic frustration. Thus, it supports the fact that the strong coupling between quadrupole and magnetic dipole moments plays important role in the exotic inverse MCE in rare-earth tetraboride system.

During the liquid metal extraction reaction between a Nd-Dy-Fe-B magnet and liquid Mg, Nd rapidly diffuses out of the magnet, whereas Dy is not extracted due to the reaction with the matrix and the formation of Dy₂Fe₁₇ phase. In addition, theDy₂O₃ phase exists at the grain boundaries. Until now, only the effect of the Dy₂O₃ phase on the extraction of Dy has been reported. In this study, the effect of the Dy₂Fe₁₇ phase on the extraction of Dy from the Nd-Dy-Fe-B magnet was investigated in liquid Mg. The formation of the Dy₂Fe₁₇ phase during the reaction between Mg and matrix (RE₂Fe₁₄B) was first examined using a thermodynamical approach and confirmed by microstructural analysis. It was observed that Dy extraction was dominated by Dy₂Fe₁₇ phase decomposition from 3 h to 24 h, followed by Dy₂O₃ phase dominant reaction with Mg. Comparing the activities of the Dy₂Fe₁₇ phase and the Dy₂O₃ phase, the reaction of Dy₂Fe₁₇ is dominant, as compared to the Dy₂O₃ phase. Finally, at 48 h, the high Dy extraction percentage of 93% was achieved. As a result, in was concluded that the Dy₂Fe₁₇ phase acts as an obstacle in the extraction of Dy. In the future, if research to control the Dy₂Fe₁₇ phase proceeds, it will be of great importance to advance the recycling of Dy.

Liquid metal extraction (LME) for recycling rare-earth elements from magnets is studied, in the present study, to examine its suitability as an environmentally friendly alternative for a circular economy. While Nd (neodymium) extraction efficiency can easily reach almost 100%, based on the high reactivity of Mg (magnesium), Dy (dysprosium) extraction has been limited because of the Dy–Fe intermetallic phase as the main extractive bottleneck. In the present paper, the boro-additive effect is designed thermodynamically and examined in the ternary and quinary systems to improve the selectivity of recovery. Based on the strong chemical affinity between B (boron) and Fe, the effect of excess boron, which is produced by the depletion of B in FeB by Mg, successfully resulted in the formation of Fe₂B instead of Dy–Fe bonding. However, the growth of the Fe₂B layer, which is the reason for the isolated Mg, leads to the production of other byproducts, rare-earth borides (RB₄, R = Nd and Dy), as the side effect. By adjusting the ratio of FeB, the extraction efficiency of Dy over 12 h with FeB addition is improved to 80%, which is almost the same extraction efficiency of the conventional LME process over 24 h.